Length is used to measure how long an object is or what is the distance between the two points. To identify the size of an object or distance between two places we need to learn how to measure length.
In this lesson we are going to learn:
Length is the amount of space between two points. Length can be measured using different techniques, tools, and units.
In earlier days people use their body parts like their hands, foot or forearm to measure the length of an object. We can use following body parts to measure the length:
Span: When the palm of our hand is spread out the distance between the tip of the little finger and the tip of the thumb is a Span.
Cubit: The distance between the elbow and tip of the middle finger is a Cubit.
Foot Span: The distance between the tip of a big toe and the end of the ankle is a Foot Span.
What will you use to measure a notebook?
We will use our hand span to measure the length of a notebook, cubit for measuring the length of a study table and foot span to measure the length of a room. Try finding out the length of your book, table and bedroom using this technique. Start from one corner and go straight to reach the other corner of the object.
Here the problem is the measurement taken by different people will vary. Our body part size are not same and therefore a need was felt to develop a standard system to measure the length.
The standard unit to measure length is meter abbreviated as m. When we divide a meter into hundred equal smaller units then each unit is equal to a centimeter abbreviated as 'cm'.
A cloth seller uses a meter rod for measuring cloth. A centimeter scale is used for measuring small objects like pencils, erasers, and books. There are many length measuring tools like measuring tape, meter scales, and rulers. We use a ruler to measure objects in centimeters.
Ruler
The above ruler can measure up to 15 cm. Each centimeter is divided into 10 equal parts called millimeters. Millimeters are abbreviated as '
Let us measure a pencil using a ruler. Keep the end of the pencil at 0 cm and mark the point where it ends.
The length of the pencil is 10 cm.
To measure the distance between two places we need a bigger unit than a meter. A kilometer abbreviated as km is used to measure the distance between two places.
The conversion of these units is shown below:
It is easy to convert units in metric to the customary system using below conversion rules.
1 inch = 2.5 cm (approx)
1 mile = 1.6 km (approx)
Question: What will be the length of a chocolate bar - 12 cm or 12 m or 12 km?
Answer: 12 cm, you can measure the chocolate bar using a ruler.
Question: What is the distance between your house and school?
(a) 2 meters (b) 2 inches (c) 2 miles
Answer: 2 miles
